Hydrogen is commonly used in various industrial applications. For example, in a fuel cell, hydrogen gas is used as a fuel to generate electrical power which operates a vehicle or other machinery. The hydrogen is typically stored in liquid form in a hydrogen tank and distributed in the liquid or gaseous phase from the tank to the fuel cell for use.
The liquid hydrogen storage system currently being used in fuel cell systems must accommodate the following requirements: (1) discharge tubes or lines which distribute liquid and/or gaseous hydrogen from the hydrogen tank; (2) two supply lines for a heater installed in the hydrogen tank; and (3) a fill tube or line. These requirements result in five tubes or lines which exit the hydrogen tank and essentially breach the integrity of the tank's thermal insulation. Currently, it is estimated that about ⅓ of the heat intrusion into the interior of the hydrogen tank is conducted via the required discharge and supply lines.
FIG. 1 illustrates a typical conventional hydrogen tank system 10 which is suitable for use in a fuel cell system. The system 10 includes a hydrogen tank 12 having multiple layers of insulation which define a tank interior 14 that contains a supply of liquid hydrogen 16. A vacuum chamber 18 outside the hydrogen tank 12 contains a gaseous hydrogen discharge valve 20, which facilitates the distribution of gaseous hydrogen from the tank interior 14, and a liquid hydrogen discharge valve 22, which facilitates the distribution of the liquid hydrogen 16 from the tank interior 14.